Silencer with flat semicylindrical expansion chamber



March 21, 1950 P. E. BESSIERE 2,501,306

SILENCER WITH FLAT SEMICYLINDRICAL EXPANSION CHAMBER Filed Aug. 25, 1947 INVENTDR Mae/MW Patented Mar. 21, 1950 SILENCER VITH FLAT SEIWICYLINDRICAL EXPANSION CHAMBER Pierre Etienne Bessire, Paris, France, assignor to Society Silto S. A., Paris, France, a society of the Republic of France Application August 25, 1947, Serial No. 770,539 In France November 21, 1946 8 Claims.

The present invention relates to devices for damping a noise propagated in a flowing fluid and it is more especially, although not exclusively, concerned with silencers for internal combustion engines and firearms.

Its chief object is to provide a device of this kind which is better adapted to meet the requirements of practice than those used for the same purpose up to this time.

Preferred embodiments of my invention will be hereinafter described with reference to the accompanying drawings, given merely by way of example and in which:

Figs. 1 and 3 to 6 show, in longitudinal section, five embodiments of silencers for internal combustion engines, made according to the invention.

Fig. 2 is a section on the line IIII of Fig. 1.

In the following description, the invention will be described as applied to the case of an exhaust silencer for an internal combustion engine.

The device is essentially constituted by at least one box I of the shape of a flat half-cylinder laterally limited partly by a plane surface 2 and partly by a surface 3 of the second order having one focus F located substantially on said plane surface.

The inlet 4 for the exhaust gases is located at said focus F. As for the outlet 5, it is located along the intersections of said surfaces 2 and 3.

Advantageously (and although the surface of the second order 3 may be of any kind whatever, provided it has one focus at F) said surface 3 is of a cylindrical shape, preferably with a semicircular base, as shown on the drawing. The radius of this base is a (Fig. 2) and the cylinder height b (b being smaller than a).

In order to lead the gases to inlet 4, I provide a conduit 6 running along plane surface 2 and which may extend over the whole height of the semi-cylindrical box.

As for outlet 5, it is provided at the intersection of surfaces 2 and 3 in line with conduit 6.

Preferably, a plurality of devices as that just above described are connected in series, the inlet of the conduit 6 of the second device communicating with the outlet 5 of the first one, and so on, the conduits 6 of the successive apparatus being in line.

Advantageously, at least one portion of the lateral walls of box I is lined with a material capable of absorbing sound, such as asbestos, glass wool, iron scale, or any other preferably uncompressed matter having good sound-proofing qualities. I may, for this purpose, locally constitute the inner wall of box I by a metal netting holding said material, which on the other side, is kept in place by a solid wall.

Thus I may provide with such a lining I, either the surface 2 of chambers I (Fig. 1), or their surfaces 3 (Fig. 3).

Likewise, as shown on Fig. 2, at least one of the faces of conduit (or conduits) t may be thus lined.

I may also provide, in the plane surface 2, of the devices in question, for instance in the central part thereof, at least one passage connecting box I with a chamber 9, such a chamber 9 being provided either for every elementary device, or (Fig. 4) a single chamber 9 being common to all the elementary devices of the same silencer. At least part of the walls of chambers t may be provided with a lining i such as above described.

In the embodiments of Figs. 1, 2 and 4, the outlet 5 is obtained b cutting out a portion of surface 3 adjacent to surface 2 of a section corresponding to that of conduit ii. However, it may be of advantage to provide an outlet of special shape such as that shown on Fig. 5, where the portion cut out in surface 3 is larger than the outlet section proper and is connected to the latter through a short conduit l0 convergent in the direction of flow of the gases.

The sound waves transmitted from inlet 4 are reflected by surface 3 toward focus F an therefore have no tendency to flow out through orifice 5, which is remote from this focus. On the other hand, these sound waves are partly absorbed when they strike a surface provided with a lining 1.

Among other advantages, the system above described ensures a direct rectilinear path for the flow of the exhaust gases, so that the pressure drop is smaller than in devices including baffles.

According to another feature of my invention, I provide the rectilinear passage constituted by the series of conduits 8 with a porous wall 1 i (Fig. 6) through which flows a portion of the exhaust gases which is subsequently evacuated through an orifice i2, without having to return into said passage.

The expression porous designates in this case, not a partition provided with holes, even of a size averaging one millimeter, but a wall constituted by a matter provided with interstices of irregular shape and size left between thin elements such as small plates, threads or filaments (asbestos, glass wool, iron scale, etc.) intertwined or juxtaposed to constitute a cushion having a substantial thickness (for instance 10 mm.) and which may be held between two metallic cloths.

Such an arrangement, although creating no supplementary resistance to the flow of gases, ensures a substantial reduction of the noise.

Of course, the invention is applicable to engine suction silencers, firearm silencers, etc.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and efficient embodiments of my invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departin from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

1. A silencer for damping noises propagated through a flowing fluid which comprises, in combination, a flat cylindrical hollow box the section of which by planes perpendicular to the cylinder generatrices is constituted partly by a portion of a straight line and partly by a por tion of a curve of the second order having its concavity turned toward said straight line portion and wholly located on one side thereof, one focus of said curve being located at least substantially on said line, an inlet conduit for said fluid parallel to said line and transverse to the cylinder generatrices, said inlet conduit having its outlet end at least substantially at said focus and an outlet for said flowing gases in the portion of the box wall in line with said inlet conduit.

2. A silencer for dampin noises propagated through a flowing fluid which comprises, in combination, a flat cylindrical hollow box the section of which by planes perpendicular to the cylinder generatrices is constituted partly by a portion of a straight line and partly by a portion of a curve of the second order having its concavity turned toward said straight line portion and wholly located on one side thereof, one focus of said curve being located close to said line, an inlet conduit for said fluid parallel to said line and transverse to the cylinder generatrices, said inlet conduit having its outlet end close to said focus and an outlet for said flowing gases in the portion of the box wall in line with said inlet conduit.

3. A silencer according to claim 1 further including a sound absorbing material forming a lining inside said box along at least a portion of the walls thereof.

4. A silencer according to claim 1 further including a sound absorbing material forming a lining inside said box along the rectilinear portion of the cylinder wall and the portions of the cylinder end walls that are adjacent to said rectilinear wall portion.

5. A silencer according to claim 2 further including a sound absorbing material forming a lining inside said box along at least a portion of the walls thereof.

6. A silencer according to claim 2 further including a sound absorbing material forming a lining inside said box along the rectilinear portion of the cylinder wall and the portions of the cylinder end walls that are adjacent to said rectilinear wall portion.

7. A silencer for damping noises propagated through a flowing fluid which comprises, in combination, a flat cylindrical hollow box of at least substantially semi-circular section and of a height smaller than its radius, an inlet conduit for said fluid parallel to the straight cylinder wall of said box and having its outlet at least substantially at the center of the circular cylinder Wall and an outlet for said flowing gases in the portion of the box wall in line with said inlet conduit.

8. A silencer for damping noises propagated through a flowing fluid which comprises, in combination, a flat cylindrical hollow box of at least substantially semi-circular section and of a height smaller than its radius, an inlet conduit for said fluid parallel to the straight cylinder wall of said box and having its outlet at least substantially at the center of the circularcylinderwall and an outlet for said flowing gases in the portion of the box wall in line with said inlet conduit, the portion of said box wall adjacent to said outlet being flat and converging toward said straight cylinder wall.

PIERRE ETIENNE BEssIERE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,101,460 Schmidt Dec. 7, 1937 2,274,459 Rauen Feb. 24, 1942 FOREIGN PATENTS Number Country Date 439,006 Great Britain Nov. 27, 1935 

